In scanners and copiers, the light used to illuminate the target area is typically provided by light emitting diodes (LEDs). As shown in FIG. 5, the light emitted from a LED 50 is spread over a large area. The light is emitted at a broad angle, with the half power point 52,53 being 80 degrees from the vertical axis 51.
Thus, most of the light produced by a LED is wasted. Consequently, scanning systems typically employ a collection lens to collect and focus the light onto the target area. As shown in FIG. 6, an LED 61 includes collection lens 63 to collect and focus the light onto target area 31. Note that LED 61 typically comprises a plurality of LEDs arranged in a single column array, and that lens 63 is a cylindrical lens. In FIG. 6, lens 33 is the SELFOC lens array from NSG. The lens 63, is typically an extruded or injection molded plastic lens, e.g. polycarbonate or acrylic. The light reflected from the surface 31 is captured by lens system 33 and focused onto detector 34. FIG. 7 depicts an alternative LED arrangement 71 that uses reflecting optics 72 to reflect the light onto the target area in place of the refracting lens 63 of FIG. 6. The light reflected from the surface 31 is captured by lens system 33 and focused onto detector 34.
The arrangements of FIGS. 6 and 7 are expensive in terms of manufacturing, as each requires additional tooling to attach the lens or reflector to the LED board. Moreover, the lens and reflectors are additional parts which increase cost. Furthermore, note that the lens 63 requires lens mount 62 to attach the lens 63 to the LED 61. This lens mount adds a space requirement to the scan system, and in smaller systems such as a hand-held scanner space is expensive. Also the arrangement of FIG. 7 is also costly in terms of space. For this arrangement to be effective, the trough formed by the reflector 72 must be deep, and thus reflector 72 protrudes from the LED board. Thus, the LED board 81 arrangement shown in FIG. 8 is typically used. Note that there is no light collection optics, instead a bare LED is used to illuminate the target area 31. The light reflected from the surface 31 is captured by lens system 33 and focused onto detector 34. Thus, most of the light produced by LED board 81 is wasted, specifically only about 0.1% of the light is used and about 99.9% of the light is wasted.
Therefore, there is a need in the art for a LED light collection system that is efficient and compact.